In the context of the present invention, traveling on the ground means any possible type of traveling of an aircraft, such as traveling on a runway during landing and take-off phases, traveling on taxiways or traveling on maneuvering areas, in particular.
When an aircraft, in particular an airplane, travels on the ground on a runway on manual pilot, the pilot steers the wheels of the front landing gear and the tail fin rudder control surface in order to follow substantially the required trajectory. This trajectory may be a straight line or a curve and may correspond in this case to a maneuver of the aircraft, for example to enter an exit road. To do this, the pilot acts on the control members (control column pedals, steering wheel to steer the front landing gear wheels), the output signals (or orders) of which are (directly) sent as instructions to the actuators of the front landing gear and of the tail fin rudder control surface.
In practice, said output signals of the control members are usually simply formatted before being sent as instructions, by appropriate functional blocks, which merely apply a variable gain to said instruction signals: for example a neutral range around the rest position, then a first gain value, then a second gain value greater than the first.
Such a mode of operation has drawbacks. In particular, it constitutes a considerable workload for the pilot who, during traveling on the ground, must constantly act on the control members steering the wheels of the front gear and the tail fin rudder control surface, in order to follow the required trajectory. This constraint is made more severe when the required trajectory is a curve. Sometimes, the pilot is required to act simultaneously on a plurality of said control members in order to follow this trajectory satisfactorily, while managing the response time of the control surfaces to a given order by means of said control members, which naturally requires constant attention on the part of the pilot which is particularly tiring.
In addition, when the traveling on the ground is done with the aid of an automatic pilot, for example when traveling on landing, a traveling law controls the actuators of the different control surfaces, as a function of the positional error of the aircraft relative to the center line of the runway, which is determined by using at least one of the various usual location means (ILS, MLS, GLS, DGPS, etc.). This traveling law has the disadvantage of being awkward to fine-tune and of being specific to the model of aircraft in question.